Question 1

Which feature of the inner mitochondrial membrane is most directly responsible for its role in ATP synthesis during oxidative phosphorylation?

Accepted Answer

High surface area due to cristae, increasing space for electron transport chain complexes

Question 2

Matrix proteins are imported into the mitochondrion through which sequence of events?

Accepted Answer

Folding by Hsp70, passage through TOM and TIM, ATP hydrolysis, and cleavage of transit sequence

Question 3

During pyruvate oxidation, which enzyme complex catalyzes the conversion of pyruvate to acetyl CoA, and what are the main products?

Accepted Answer

Pyruvate dehydrogenase complex; products are acetyl CoA, CO$_2$, and NADH

Question 4

Which of the following best explains why aerobic respiration is more efficient than fermentation?

Accepted Answer

Aerobic respiration uses oxygen as the final electron acceptor, allowing complete oxidation of glucose

Question 5

In the citric acid cycle, the exergonic hydrolysis of the thioester bond in succinyl CoA is coupled to the synthesis of which molecule in animal cells?

Accepted Answer

GTP

Question 6

Which regulatory mechanism controls the activity of pyruvate dehydrogenase in response to cellular energy levels?

Accepted Answer

Phosphorylation inactivates the enzyme when ATP levels are high

Question 7

Beta-oxidation of fatty acids produces more energy than carbohydrate metabolism primarily because:

Accepted Answer

Fatty acids are more highly reduced, yielding more NADH and FADH$_2$ per molecule

Question 8

Which of the following is the correct sequence of the five stages of aerobic respiration?

Accepted Answer

Glycolysis, pyruvate oxidation, citric acid cycle, electron transport chain, oxidative phosphorylation

Question 9

A mutation in the mitochondrial DNA affecting the inner membrane protein polypeptides would most likely impact which process?

Accepted Answer

Electron transport chain function

Question 10

Which of the following statements about the transport of pyruvate into the mitochondrion is correct?

Accepted Answer

Pyruvate is transported into the mitochondrial matrix via a specific carrier protein, driven by the proton gradient

Question 11

Which of the following is a direct product of the citric acid cycle per acetyl CoA molecule oxidized?

Accepted Answer

3 NADH, 1 FADH$_2$, 1 ATP/GTP, and 2 CO$_2$

Question 12

Allosteric regulation of the citric acid cycle is primarily achieved by which molecule acting as a feedback inhibitor?

Accepted Answer

NADH

Question 13

Which process is responsible for the breakdown of triacylglycerols into fatty acids and glycerol before beta-oxidation?

Accepted Answer

Hydrolysis

Question 14

During beta-oxidation, what is the fate of the two-carbon units removed from fatty acids?

Accepted Answer

They are converted to acetyl CoA and enter the citric acid cycle

Question 15

Which of the following best describes the role of chaperone proteins such as Hsp70 in mitochondrial protein import?

Accepted Answer

They maintain proteins in an unfolded state for translocation through TOM and TIM complexes

Question 16

Which step in the citric acid cycle involves the formation of a C=C double bond and the reduction of FAD to FADH$_2$?

Accepted Answer

Oxidation of succinate to fumarate

Question 17

Which of the following is NOT a function of the mitochondrial matrix?

Accepted Answer

Site of glycolysis

Question 18

A patient presents with a mitochondrial disorder affecting the import of matrix proteins. Which cellular process is most likely impaired?

Accepted Answer

ATP synthesis via oxidative phosphorylation

Question 19

Which of the following statements about the regulation of the citric acid cycle is correct?

Accepted Answer

High levels of NADH inhibit dehydrogenase enzymes, slowing the cycle

Mitochondrial Structure and Cellular Respiration: Pyruvate Oxidation, Citric Acid Cycle, and Fatty Acid Catabolism

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